Grapefruit and Grapefruit Juice Interactions with Drugs

by Health Canada

Certain drugs can cause serious or occasionally life-threatening effects if consumed in combination with grapefruit or its juice.

Consuming grapefruit or its juice (fresh or frozen) can increase, or less commonly decrease, the effects of some drugs. There are several substances in grapefruit that interfere with the way your body handles certain drugs.

These effects are known to be caused by the combination of grapefruit and its juice with certain drugs and health products used in the treatment of medical conditions, including, but not limited to:

• Angina
• Anxiety
• Cancer
• Convulsions
• Depression
• Erectile dysfunction
• Gastrointestinal reflux
• High blood pressure
• High lipid (cholesterol) levels
• HIV/AIDS
• Infections
• Irregular heart rhythms
• Organ graft rejections
• Psychotic problems

Sour oranges, such as Seville, or their juice, may have an effect similar to grapefruit juice. Most other citrus fruits, such as lemons, limes, citrons, naturally sweet oranges and tangerines are not thought to have this effect. However, tangellos, a hybrid of grapefruit, may also interfere with drugs.

How Grapefruit and Its Juice React with Certain Medications

There are substances in grapefruit that can interfere with the way your body absorbs and breaks down (metabolizes) certain drugs. This interference allows a higher amount of the drug than usual to circulate in your bloodstream, which can occasionally result in serious or life-threatening adverse reactions.

As little as one glass of grapefruit juice (8 oz. or 250 mL) can cause an increased blood drug level and the effects can last for three days or more. Therefore, even if you drink the juice in the morning and do not take your medication until bedtime, the level of the drug in your blood could still be affected.

The effects vary from one person to another, from one drug to another, and from one grapefruit juice preparation to another. This results in an unpredictable increase in blood drug level, which in some cases can cause serious effects.

Minimizing Your Risk

Take the following precautions to minimize the risk of adverse effects when consuming grapefruit or its juice:

• If you are taking medication for any of the conditions listed above, DO NOT drink grapefruit juice or eat grapefruit in any form until you have talked to your doctor and your pharmacist about the potential for an adverse reaction.
• Avoid taking any drug with grapefruit juice until you have talked to your doctor or pharmacist.
• Read the labels on foods and natural health products to make sure they do not contain grapefruit or its juice, or Seville oranges.
• Always report any adverse drug reaction to your doctor or pharmacist immediately.

How the Government of Canada is Protecting Your Health

Health Canada has issued several communication documents to remind health care providers of possible interactions between grapefruit and drugs. In addition, Health Canada is working with the drug manufacturers whose products are adversely effected by grapefruit, to ensure that the needed information is placed on the product label. A public advisory has been issued on grapefruit and its effect on certain drugs.

About the Author

www.hc-sc.gc.ca
Health Canada is the Federal department responsible for helping Canadians maintain and improve their health, while respecting individual choices and circumstances.